T-Cell Lymphomas in Mexico: Experience of a Third Level Reference Hospital

Introduction ------- Mature T-cell lymphomas have a global incidence ranging from 9.3% to 13.4% of the total amount of non-Hodgkin lymphomas worldwide. However, in Asian and South and Central America countries, incidence has been reported up to 20%. This suggests that there is a wide range of environmental and racial factors that modify the frequency of T-cell lymphomas and its subtypes. The common subtypes of these lymphomas also have been reported to vary greatly across the world. Studies have placed the NK/T cell lymphoma as the most prevalent T-cell lymphoma of Mexico, with 40% of all T cell lymphomas diagnosed, while the US reported frequency ranges in the 5 to 6%. Our objective is to report our experience in a third level reference Hospital in northeast Mexico.

Materials and Methods ---- A retrospective and observational study was conducted. Utilizing the database manager Pathox, we collected all the cases of patients diagnosed with lymphoma from January 2010 to January 2017. We included in the study all cases that were diagnosed with a variant of T-cell lymphoma that had available material for revision. They were assigned to groups by sex, subtype of lymphoma in accordance to the World Health Organization (WHO) classification of lymphoid neoplasms 2016, and the anatomical location of the primary tumor. Data analysis was performed in the statistical programming environment R version 3.3.2. Descriptive statistics were reported as percentages, central tendency and dispersion statistics.

Results --------- We found a total of 771 lymphomas in our study. 88 of those had a diagnosis of T-cell lymphoma. The location of the primary tumor was a lymph node in 36.26% of the cases, and in the rest of the primary tumors, the skin was the most frequent location with 57.14%; the nasal and retronasal tissue followed, with 5.49%. For the subtypes, the most frequent was mycosis fungoides (MF) (29.67%) followed by Peripheric T-cell Lymphoma, Not Otherwise Specified, (PTCL, NOS) (23.08%). NK/T-Cell lymphoma nasal type, accounted for 10.99%. Anaplastic Large Cell Lymphoma (ALCL) ALK+ (4.4%), ALCL ALK - (7.69%), Angioinmunoblastic T-cell lymphoma (AITL) (2.20%) and subcutaneous Panniculitis- like T-cell lymphoma (1.1%) were also reported. The rest of the cases were reclassified into a non T-cell lymphoma or different diagnosis. Of the IHQ stains used to for diagnosis, the most commonly used were CD20, CD4, CD3, CD7 and CD8, with an average number of IHQ stains of 4.4 per case.

Conclusions --- Available literature places the frequency of T-cell lymphomas between 5 and 15% for developed countries, in concordance to our frequency (11.4%). For anatomic location of the primary tumor, the most frequent location was the skin (57.14%), followed by the lymph nodes (36.26%) and the nasal tissue (5.49%), while the rest distributed among the bone marrow, soft tissues, and tonsils. Frequency was not significant among males or females. Subtype frequency predominated for MF (29.67%) and PTCL, NOS (23.08%). NK/T-cell lymphomas account for only 10.99%. Our data suggests that the environmental, geographical and race factors create wide variations in the frequency of these lymphomas and their subtypes, giving way for additional studies to find and explain this variations.